Such a process is known from the European Patent Application No. 0,072,010. In said known process use is made of the L. bulgaricus strain DSM 2129 which appears to be capable of producing D-(-)-lactic acid in high yield in a relatively short time from lactose or glucose. It appears from the description, however, that the strain is not capable of producing acid from galactose, which means that only the glucose part of the lactose is used for the production of the lactic acid and the galactose part remains unchanged.
Hitherto, no strains of Lactobacillus species were known which are galactose-positive and produce D-(-)-lactic acid almost exclusively. It is true that it is reported in Bergey's Manual of Determinative Bacteriology (8th edition) that L. bulgaricus is galactose-positive and produces D-(-)-lactic acid almost exclusively, but later investigation revealed that the type strain ATCC 11842 cannot convert any galactose into acid [J. Gen. Microbiol. 74, 289-297 (1973)]. Furthermore, it appears from Appl. Environm. Microbiol. 45, 1932-1934 (1983) that strains of L. helveticus and L. bulgaricus which are galactose-positive always produce a mixture of D- and L-lactic acid in which the L-isomer predominates, and that strains of L. lactis and L. bulgaricus which are galactose-negative always produce D-(-)-lactic acid almost exclusively.